getting not on common subnet in cisco 6509 (using VRRP)

Unanswered Question
Sep 16th, 2008

hi, got a message from 2 core switch 6509:

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.17.2 not on common subnet for Vlan3

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.16.50 not on common subnet for Vlan8

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.16.50 not on common subnet for Vlan8

i thought the problem was because their interconnection was disconnected. i had them connected and i still get the message error on the both core switch.

i have used: clear ip eigrp neigh

clear ip route *

and log still persist.

any idea why?

the eigrp configuration was not changed

eigrp 109

10.0.0.0

the vrrp is ok

interface Vlan3 (cisco 6509)

ip address 10.100.22.54 255.255.255.0 secondary

ip address 10.100.16.50 255.255.255.0

ip helper-address 10.100.18.9

ip helper-address 10.100.18.13

no ip redirects

ip wccp 61 redirect in

vrrp 3 ip 10.100.16.254

vrrp 3 ip 10.100.22.254 secondary

vrrp 3 preempt delay minimum 5

vrrp 3 priority 150

end

interface Vlan3 (cisco 6509)

ip address 10.100.22.54 255.255.255.0 secondary

ip address 10.100.16.40 255.255.255.0

ip helper-address 10.100.18.9

ip helper-address 10.100.18.13

no ip redirects

ip wccp 61 redirect in

vrrp 3 ip 10.100.16.254

vrrp 3 ip 10.100.22.254 secondary

vrrp 3 preempt delay minimum 5

vrrp 3 priority 150

end

interface Vlan8

ip address 10.100.17.6 255.255.255.0

ip helper-address 10.100.18.9

ip helper-address 10.100.18.1

vrrp 8 ip 10.100.17.254

vrrp 8 preempt delay minimum 5

end

I have this problem too.
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lgijssel Tue, 09/16/2008 - 03:37

This has little to do with vrrp. You get this message when two connected interfaces running eigrp are using different ip subnets.

The conflicting device is identified as the neighbor and the message also tells you the vlan where the mismatch is detected.

Looking at the logs, my conclusion is that the ip adresses for vlan3 and vlan8 are configured in opposite order as on the device shown.

regards,

Leo

Richard Burts Tue, 09/16/2008 - 04:38

Eduard

Perhaps Leo is correct that it is a configuration error with addresses in opposite order. But I wonder in looking at these messages:

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.17.2 not on common subnet for Vlan3

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.16.50 not on common subnet for Vlan8

*Sep 16 18:54:38.141 gmt: IP-EIGRP(Default-IP-Routing-Table:109): Neighbor 10.100.16.50 not on common subnet for Vlan8

and noticing that VLAN 3 is complaining about an address belonging to VLAN 8 and that VLAN 8 is complaining about an address in VLAN 3, then it makes me wonder if someone has changed a connection so that VLAN 3 and VLAN 8 are now connected in some manner. That would be consistent with your statement that the configuration was not changed. I wonder if the output of show cdp neighbor and of show vlan 3 and show vlan 8 might help us find the issue.

HTH

Rick

edongskiu Tue, 09/16/2008 - 05:19

hi rick, only the int giga 5/2 between the core switch were disconnected but were able to plug it back.

i shutdown the vlan interface of vlan 8 and 3 on core switch 2 and the logs were gone on coreswitch 2, however, on core switch 1 the logs persist.

i even shutdown both vlan and activate it back, but to no avail the log persist

Richard Burts Tue, 09/16/2008 - 05:46

Eduard

If the errors stop on switch 2 when you shut down both VLANs, do the errors stop if you shut down only a single VLAN?

I continue to wonder if the issue is that someone has connected something that is interconnecting VLAN 3 and VLAN 8. Perhaps a hub or perhaps a switch with an access port in VLAN 3 and another access port in VLAN 8. Can you post the output of show cdp neighbor as a starting point to investigate this?

HTH

Rick

edongskiu Tue, 09/16/2008 - 06:03

hi rick, of the two errors, one will stop if one of the affected vlan was shutdown.

i have checked both of them and none have other switch connected aside from both of them and 3750

Attachment: 
Richard Burts Tue, 09/16/2008 - 09:06

Eduard

Thank you for the output of show cdp neighbor. Would you also post the output of show vlan on both 6509 and the configuration of the interfaces gig 2/0/11, 2/0/12, 3/0/23, and 3/0/24 from the 3750.

HTH

Rick

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